1. Industrial Applicability
This invention relates to a high resolution image pickup device, particularly an image pickup device having a high resolution, which is capable of recording and erasing optical image information utilizing a rewritable recording member.
2. Prior Art
Since a video signal either in a state of real time signal or stored signal obtained as a result of picking up electronically an image of an object has features of post-production conveniences i.e. editing and trimming of pictures, and other image signal processing are easy, and recording, erasing and reproduction of the video signal on and from conventional materials are quite feasible, such utilization thereof has been made in many fields, e.g., printing, electronic publishing and measurement fields, etc. in addition to the broadcasting field. However, in such applications, it has been strongly desired to develop a device capable of image pick up and recording of considerably high resolution pictures which may be optical image information charging time sequentially such as moving pictures, or still pictures.
In image pickup devices which have been typically used heretofore, an optical image of an object is formed on the photoelectric conversion section of the image pickup element by an imaging lens, and the optical image of the object is converted to electric image information in the image pickup element, thereafter to output the electric image information thus obtained as a continual video signal in the time domain. It is well known that various image pickup tubes and various solid state image pickup elements are used as an image pickup unit which is to be used in constituting the image pickup device.
3. Problems to be solved by the Invention
For obtaining a high picture quality and high resolution reproduced image, an image pickup device capable of producing a video signal corresponding thereto is required. In an image pickup device using an image pickup tube as the image pickup sensor, it is difficult to generate such a video signal capable of rendering a high picture quality and high resolution reproduced image because of the fact that there is a limitation in reduction of the diameter of the electron beam in the image pickup tube due to a performance limitation of the electron gun and the associated focus system structure, so that development of high resolution image pickup tube based on the reduction of the diameter of the electron beam cannot be expected. As an alternative, an increase of the target area of the image pickup tube is conceivable, but it requires a large optional system, and as a capacitance of the target of the image pickup tube increases in proportion to the target area, increase of the target area causes inevitably an attenuation of high frequency components in the output video signal. It should be noted that in the case of a high resulution image pickup device for a moving picture, the frequency range of the video signal would become more than several tens of MHz to several hundreds MHz, resulting in the problem of S/N ratio degradation, and the like.
Accordingly, it is unrealistic to develop the high resolution image pickup tube based on the reduction of the diameter of the electron beam or the increase of the target area.
Further, for providing a high picture quality and high resolution reproduced image by means of an image pickup device using solid state elements as the image pickup sensor, it is required to use a solid state image pickup element having a considerably large number of pixels. In the case of such a solid state image pickup element having a large number of pixels, the clock frequency for driving it would become extremely high (e.g., the clock frequency for driving the solid state image pickup element in the case of a moving picture camera becomes equal to several hundreds MHz), and the electrostatic capacitance of the circuit to be driven becomes large with an increase in the number of pixels, it is considered that such a solid state image pickup device cannot be constructed practically in the present circumstances where the limitation of the clock frequency of the solid state image pickup element is said to be 20 MHz.
As just described above, since conventional image pickup devices could not satisfactorily generate such a video signal capable of rendering high picture quality and high resolution reproduced image because of existence of image pickup sensors indispensable for the construction thereof, it is desired that an advent of image pickup device capable of satisfactorily generating such a video signal capable of rendering a high picture quality and high resolution reproduced image. Further, in many industries, e.g., printing, electronic publishing, measurement industries are expecting as their tool, electronic picture processing equipment utilizing video signals with which picture editing, trimming, and other image processing are easy, also recording/reproduction and recording/reproduction/erasing of an image having a high resolution are easily conducted using a recording member having an erasable and rerecordable property. It is also highly expected that an advent of image pickup device which can produce a recorded still or single picture having an extremely high a resolution.
For this purpose, there is proposed a charge image recording medium on which an electrostatic latent image corresponding to information to be recorded and reproduced is formed. In this type of the charge image recording medium, since the recorded image is on the exposed surface of the medium, the image is subject to deterioration, e.g. there is a preservation problem. For this reason, an attempt has been made to use a charge image recording medium such that an electrostatic latent image corresponding to information to recorded and reproduced is formed therewithin.
In order to use such an electric charge image recording medium repeatedbly as an erasable and rerecordable medium, there is desired means or method of erasing the recorded charge image formed even inside the recording medium. It has been needed that the above-mentioned recording medium can be repeatedly used as a reversible recording medium. For this reason, there has been required means for erasing an electrostatic latent image recorded in a charge image recording medium constituted so that an electrostatic latent image is formed in the electric.